The increasing integration of LSIs has led to finer and finer circuit line widths of semiconductor devices. An approach employed to form desired circuit patterns on semiconductor devices uses a step-and-repeat exposure system to reduce and transfer, onto a wafer, a high-precision master pattern (also called a mask, or a reticle particularly when used in a stepper or scanner) formed on a piece of quartz. The high-precision original pattern is written with an electron beam writing apparatus by use of a so-called electron beam lithography technique.
For example, there are writing apparatuses that use multiple beams. The use of multiple beams can greatly improve the throughput because it enables irradiation with more beams at a time (in a single shot) than in the case where writing is performed using a single electron beam. In such multi-beam writing apparatuses, for example, multiple beams are formed by letting an electron beam emitted from an electron gun pass through an aperture member having a plurality of apertures. Blanking control is performed on each of the beams. Unblocked beams are each reduced by an optical system, and a substrate placed on a movable stage is irradiated with the resulting beams.
In an aperture member that forms multiple beams, holes in m columns×n rows (where m, n≥2) are formed at predetermined array pitch in a matrix. Thus, the shape (aperture image) of the overall multiple beams with which a substrate is irradiated is ideally a rectangular shape. However, under the influence of spherical aberration of an electron optical system provided with a writing apparatus, a shape where four sides on the outer edge of the beam shape project outside or a shape where the four sides are depressed inside may be caused.
It has been difficult to assess such specific beam shapes and automatically adjust spherical aberration.